全文获取类型
收费全文 | 4457篇 |
免费 | 73篇 |
国内免费 | 10篇 |
专业分类
化学 | 3179篇 |
晶体学 | 20篇 |
力学 | 71篇 |
数学 | 937篇 |
物理学 | 333篇 |
出版年
2019年 | 34篇 |
2016年 | 71篇 |
2015年 | 52篇 |
2014年 | 37篇 |
2013年 | 115篇 |
2012年 | 89篇 |
2011年 | 143篇 |
2010年 | 102篇 |
2009年 | 118篇 |
2008年 | 142篇 |
2007年 | 146篇 |
2006年 | 151篇 |
2005年 | 134篇 |
2004年 | 111篇 |
2003年 | 103篇 |
2002年 | 104篇 |
2001年 | 56篇 |
2000年 | 72篇 |
1999年 | 62篇 |
1998年 | 61篇 |
1997年 | 56篇 |
1996年 | 76篇 |
1995年 | 79篇 |
1994年 | 60篇 |
1993年 | 71篇 |
1992年 | 100篇 |
1991年 | 95篇 |
1990年 | 78篇 |
1989年 | 72篇 |
1988年 | 65篇 |
1987年 | 65篇 |
1986年 | 69篇 |
1985年 | 84篇 |
1984年 | 92篇 |
1983年 | 84篇 |
1982年 | 83篇 |
1981年 | 109篇 |
1980年 | 61篇 |
1979年 | 80篇 |
1978年 | 74篇 |
1977年 | 93篇 |
1976年 | 65篇 |
1975年 | 81篇 |
1974年 | 85篇 |
1973年 | 64篇 |
1972年 | 55篇 |
1971年 | 48篇 |
1970年 | 37篇 |
1967年 | 31篇 |
1962年 | 29篇 |
排序方式: 共有4540条查询结果,搜索用时 15 毫秒
181.
Goren AC Hrovat DA Seefelder M Quast H Borden WT 《Journal of the American Chemical Society》2002,124(13):3469-3472
Time-dependent B3LYP/6-31G calculations have been performed at the optimized C(2) or C(2v) geometries of several substituted semibullvalenes (1(deloc)) and barbaralanes (2(deloc)), to compare the computed vertical electronic excitation energies with the temperature-dependent, long-wavelength absorptions that have been observed in the UV/vis spectra of some of these compounds by Quast and co-workers. The excellent agreement between the calculated vertical excitation energies and the observed values of lambda(max) provides strong support for the identification of the bishomoaromatic species 1(deloc) and 2(deloc) as the source of these absorptions. Furthermore, the CN stretching frequencies, computed for the C(2) geometry of 1,5-dimethyl-2,6-dicyano-4,8-diphenylsemibullvalene (1f(deloc)), fit the low-frequency absorptions seen in the IR spectrum of 1f, thus furnishing independent evidence that bishomoaromatic geometries of semibullvalenes have, in fact, been observed spectroscopically. B3LYP/6-31G calculations predict that 2,6-dicyano-4,8-diphenylsemibullvalene 1c has a C(2) equilibrium geometry (1c(deloc)) and that the long-wavelength UV/vis absorption (lambda(max) = 585 nm) and CN stretching frequencies (2192 and 2194 cm(-1)) computed for 1c(deloc) should serve to identify this bishomoaromatic semibullvalene when it is synthesized. 相似文献
182.
Helmut Strasser 《Journal of multivariate analysis》1975,5(2):206-226
Let (X, ) be a measurable space, Θ ? an open interval and PΩ ∥ , Ω ? Θ, a family of probability measures fulfilling certain regularity conditions. Let be the maximum likelihood estimate for the sample size n. Let λ be a prior distribution on Θ and let be the posterior distribution for the sample size n given . denotes a loss function fulfilling certain regularity conditions and Tn denotes the Bayes estimate relative to λ and L for the sample size n. It is proved that for every compact K ? Θ there exists cK ≥ 0 such that This theorem improves results of Bickel and Yahav [3], and Ibragimov and Has'minskii [4], as far as the speed of convergence is concerned. 相似文献
183.
184.
185.
186.
187.
Afshin Nabiyan Johannes Bernhard Max Dr. Christof Neumann Magdalena Heiland Prof. Dr. Andrey Turchanin Prof. Dr. Carsten Streb Prof. Dr. Felix Helmut Schacher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16924-16929
An effective strategy to enhance the performance of inorganic semiconductors is moving towards organic-inorganic hybrid materials. Here, we report the design of core–shell hybrid materials based on a TiO2 core functionalized with a polyampholytic (poly(dehydroalanine)-graft-(n-propyl phosphonic acid acrylamide) shell (PDha-g-PAA@TiO2). The PDha-g-PAA shell facilitates the efficient immobilization of the photosensitizer Eosin Y (EY) and enables electronic interactions between EY and the TiO2 core. This resulted in high visible-light-driven H2 generation. The enhanced light-driven catalytic activity is attributed to the unique core–shell design with the graft copolymer acting as bridge and facilitating electron and proton transfer, thereby also preventing the degradation of EY. Further catalytic enhancement of PDha-g-PAA@TiO2 was possible by introducing [Mo3S13]2− cluster anions as hydrogen-evolution cocatalyst. This novel design approach is an example for a multi-component system in which reactivity can in future be independently tuned by selection of the desired molecular or polymeric species. 相似文献
188.
189.
Helmut M. Hügel 《合成通讯》2013,43(12):1075-1080
A convenient four step procedure for the synthesis of benoxaprofen is described starting with 4-hydroxyphenylacetic acid. 相似文献
190.